Pull Up: Java -> Kotlin interoperability

#KT-5803 Fixed

idea/idea-core/src/org/jetbrains/kotlin/idea/core/psiModificationUtils.kt

@@ -148,4 +148,9 @@ private fun deleteElementWithDelimiters(element: PsiElement) {
 
 public fun PsiElement.deleteSingle() {
     CodeEditUtil.removeChild(getParent()?.getNode() ?: return, getNode() ?: return)
+}
+
+public fun JetClass.getOrCreateCompanionObject() : JetObjectDeclaration {
+    getCompanionObjects().firstOrNull()?.let { return it }
+    return addDeclaration(JetPsiFactory(this).createCompanionObject()) as JetObjectDeclaration
 }